Smoke rises from the direction of the Tripoli, Libya, airport in an image captured from a video on July 13, 2014. The United States shut down its embassy in Libya on July 26, 2014. / AP

by Mathieu Galtier and Luigi Serenelli, Special for USA TODAY

by Mathieu Galtier and Luigi Serenelli, Special for USA TODAY

TRIPOLI, Libya - Libya appealed for international help Monday after an oil depot was set on fire during severe fighting between rival militias at Tripoli's international airport in the worst level of violence since the 2011 revolution that ousted Moammar Gadhafi.

The interim government said that fighting between rival militias caused the blaze at the depot, which contains 1.6 million gallons of petroleum and could trigger a "humanitarian and environmental disaster," the government said in a statement.

Libya's state-run National Oil Corp. said on its Facebook page that the government had contacted "several (foreign) states asking if they were willing to send planes and teams specializing in fire extinguishing."

The battle for control of the airport erupted two weeks ago when Islamist-led militias, mainly from the western city of Misrata, tried to wrest control of the area from a rival militia from the town of Zintan.

Over the weekend, the United States and Britain evacuated their embassies in Libya and transferred the staff to Tunisia, because of safety concerns as the conflict escalates. On Monday, Germany pulled out its embassy staff in Tripoli.

Other western countries such as Germany, the Netherlands and France urged their citizens to leave Libya.

In 2012, U.S. Ambassador Christopher Stevens and three other Americans were killed in an attack in Benghazi - Libya's second-largest city.

Libya has been plagued with factional fighting since the United States and NATO launched air operations to oust Gadhafi. In the past year, that violence has escalated in the absence of a strong federal government and united military that could keep control over the security situation and bring the various militias and other factions together.

Some expect the fighting to escalate, because a militia made up of the ethnic Tubu tribe in the city of Murzuk, which answers to the Libyan Military of Defense, is threatening to intervene if the attack continues.

"All revolutionary brigades and army units in the south are ready to intervene militarily to protect the airport and enforce peace at all costs," said Barka Wardougou, who heads the military council in Murzuk in southern Libya, a stronghold of the Tubu, and supports the Zintanis. "I warn the militias who are carrying out an assault on Tripoli International Airport and deliberately destroying the national properties that we will not stand aside and watch in silence. We will move if the assaults on the airport continue."

Lawmakers said the militants are trying to make a power grab by preventing parliament from meeting.

"Islamists want to control the airports in order to prevent members of the House of Representatives from meeting in Benghazi (where the new parliament is housed)," said Ali Tekbali, a newly elected member of Libya's House of Representatives and a staunch opponent of the Islamists.

Violence has been escalating in the country recently with the Libyan Health Ministry saying clashes between rival groups have killed 79 people and wounded more than 400 in the past few weeks. Over the weekend, 32 people were killed and 62 wounded, the ministry said.

Some residents said the situation reminds them of the early 1990s, when the United Nations imposed sanctions to pressure Libya into handing over those suspected of being involved in the 1988 bombing of the Pan Am jetliner over Lockerbie, Scotland, which killed 270 people. Then, it was difficult to fly out of Libya.

"We are back to the period of embargo in the beginning of the 1990s," said Nabil Suleiman, chairman of a Libyan association of entrepreneurs, about the closure of the airport. "I remember I used to travel in the cargo boats with my goods to Malta. And from there, I could take a plane to where I wanted."